What does comparative embryology reveal about different groups of organisms?

Comparative embryology reveals that embryos of different groups of organisms share similarities during certain stages of development. This observation supports the idea that these organisms have a common ancestry, as early developmental stages often exhibit structural resemblances despite eventual divergence into distinct species. For instance, many vertebrate embryos display similar features such as notches that develop into gill structures, indicating a shared evolutionary origin. This aspect highlights the importance of embryological development in understanding evolutionary biology, reinforcing the idea that seemingly different organisms can have common traits at an early stage of their life cycle.